1. Field of the Invention
The present invention relates to a bending operation apparatus for an endoscope that is provided in an operation portion of the endoscope and causes a bending portion of an insertion portion of the endoscope to bend, and to the endoscope including the bending operation apparatus.
2. Description of the Related Art
In recent years, endoscopes have been widely used in the medical field and the industrial field. The endoscope for use in the medical field is capable of observing organs in a body cavity with an elongated insertion portion inserted into the body cavity that is a subject. The endoscope for use in the medical field is also capable of performing various treatments by using as necessary a treatment instrument inserted into an insertion channel included in the endoscope.
With the endoscope for use in the industrial field, the elongated insertion portion of the endoscope can be inserted into an object such as a jet engine and pipes in a factory, thereby allowing to perform inspections such as observations of scratches and corrosions of a region to be inspected in the object, and various treatments with respect to the region to be inspected in the object.
A configuration is well-known in which a bending portion bendable in plural directions is provided to the insertion portion of the endoscope. The bending portion improves the advanceability of the insertion portion in a crooked portion in a duct and renders variable the observation direction of an observation optical system provided at a distal end portion located on a distal end side in an inserting direction with respect to the bending portion (hereinafter referred to as “distal end side”), in the insertion portion.
The bending portion provided at the insertion portion of the endoscope is typically configured to be bendable in four directions, for example, up, down, right and left directions, with a plurality of bending pieces being connected along the inserting direction of the insertion portion. The bending portion is bendable in any of the up, down, right and left directions by a bending operation apparatus provided in an operation portion pulling any of four wires which are inserted through in the insertion portion and which have distal ends in the inserting direction (hereinafter referred to as “distal ends”) fixed to a bending piece located on the distal-most end side of the bending pieces.
Specifically, the bending portion has a configuration in which an up-and-down bending sprocket provided in the operation portion is pivoted through a pivoting operation by a bending operation knob for up-and-down bending provided in the operation portion, to pull an upside chain part or a downside chain part of an up and down bending chain wound around the sprocket, thereby pulling an upper or lower wire so that the bending portion is bent in either an up or down direction.
Further, the bending portion has a configuration in which a right-and-left bending sprocket provided in the operation portion is pivoted through a pivoting operation by a bending operation knob for right-and-left bending provided in the operation portion, to pull a right chain part or a left chain part of a right-and-left bending chain wound around the sprocket, thereby pulling a right or left wire, so that the bending portion is bent in either a right or left direction.
A configuration is also well-known in which the operation portion is provided with an up-and-down bending lock lever that fixes a bending angle of the bending portion that is bent in an up or down direction by the pivoting operation of the bending operation knob for up-and-down bending, namely, fixes the pivoting position of the bending operation knob for up-and-down bending. A configuration is also well-known in which the operation portion is provided with a right-and-left lock knob that fixes the bending angle of the bending portion that is bent in a right or left direction by the pivoting operation of a bending operation knob for right-and-left bending, namely, fixes the pivoting position of the bending operation knob for right-and-left bending. The configurations of the lock knob are disclosed in Japanese Patent Application Laid-Open Publication No. 10-286220, for example.
Japanese Patent Application Laid-Open Publication No. 10-286220 discloses a configuration in which the space inside the bending operation knob for up-and-down bending is provided with a friction member that comes into contact with an inner circumferential surface of the knob, and a movable member and a fixed member which are capable of sandwiching the friction member and fixed to the up-and-down lock lever.
When the pivoting position of the bending operation knob for up-and-down bending is fixed using the configuration disclosed in Japanese Patent Application Laid-Open Publication No. 10-286220, the up-and-down lock lever is rotated in one direction along with the lock lever to move the movable member with respect to the fixed member by employing a screw mechanism, to cause the friction member to be sandwiched between the fixed member and the movable member to be elastically deformed, so that the friction member is caused to come into contact with the inner circumferential surface of the bending operation knob for up-and-down bending by a frictional force. Thus, the pivoting position of the bending operation knob for up-and-down bending is fixed by the frictional force.
Note that in Japanese Patent Application Laid-Open Publication No. 10-286220, the configuration in which the pivoting position of the bending operation knob for right-and-left bending is fixed is similar to the configuration in which the pivoting position of the bending operation knob for up-and-down bending is fixed.
Such a configuration for a small bending operation apparatus may also be possible in which the pivoting position of the bending operation knob can be properly fixed with a weak force without a positional variation every time the bending operation knob is used, by using cam grooves instead of the screw mechanism to move two movable disks so as to have a small gap between the movable disks, so that the movable disks sandwich a fixed disk that applies a frictional force to the pivoting of the bending operation knob.